Slurry for use in polishing semiconductor device conductive structures that include copper and tungsten and polishing methods

ABSTRACT

A method for substantially simultaneously polishing a copper conductive structure of a semiconductor device structure and an adjacent barrier layer. The method includes use of a polishing pad with a slurry solution in which copper and a material, such as tungsten, of the barrier layer are removed at substantially the same rate. The slurry is formulated so as to oxidize copper and a material of the barrier layer at substantially the same rates. Thus, copper and the barrier layer material have substantially the same oxidation energies in the slurry. Systems for substantially polishing copper conductive structures and adjacent barrier structures on semiconductor device structures are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a is a Continuation of U.S. patent application Ser.No. 09/653,392, filed Aug. 31, 2000, now U.S. Pat. No. 6,551,935.

FIELD OF THE INVENTION

The present invention relates generally to slurries that are useful inchemical-mechanical polishing or chemical mechanical planarizationprocesses and, more specifically, to slurries that are used to polish orplanarize electrically conductive structures of semiconductor devicesthat include copper and an adjacent tungsten-containing barrier. Thepresent invention also relates to methods for substantially concurrentlypolishing or planarizing structures formed from copper and tungsten.

BACKGROUND OF THE INVENTION

CMP

Chemical-mechanical polishing and chemical-mechanical planarization,both of which are referred to in the art as “CMP”, are abrasivetechniques that typically include the use of a combination of chemicaland mechanical agents to planarize, or otherwise remove material from orplanarize a surface of a semiconductor material substrate during thefabrication of devices thereon. A chemical component, typically a slurrythat includes one or more oxidizers, abrasives, complexing agents, andinhibitors, oxidizes the surface of one or more material layers that arebeing polished or planarized (i.e., at least partially removed). Apolishing pad formed from a material such as polyurethane or acrylic isused with the slurry and, in combination with abrasives present in theslurry, effects mechanical removal of the layer or layers from thesurface of the semiconductor device structure. It should be noted thatabrasive-only polishing and planarization, e.g., without the use ofactive chemical agents to effect material removal, are becoming moreprevalent due to environmental concerns. Thus, the term “CMP” as usedherein encompasses such abrasive-only (i.e., strictly mechanical)methods and apparatus.

Copper Conductive Structures

The use of copper as a conductive material in semiconductor devices isalso ever increasing. When copper is used in semiconductor devices,however, a barrier layer is typically required between the copper andadjacent structures or layers. The barrier layer prevents diffusion ofthe copper into the adjacent layers or structures, as well as theformation of copper silicides, both of which may cause electrical shortsin semiconductor devices that include copper. Tantalum is an example ofa material that is useful as a copper barrier. When tantalum is used,the semiconductor device, including any features thereof into whichcopper is to be disposed (e.g., trenches), is lined with a layer oftantalum. The tantalum layer is then typically covered with a thincopper layer, often formed by physical vapor deposition (“PVD”)processes. The thin copper layer then acts as a so-called “seed layer”for the formation of a copper structure, such as a conductive line, suchas by electroplating processes.

Once the tantalum and copper layers have been formed, it is necessary toisolate separate tantalum-copper conductive structures from one another.CMP processes are typically used to remove the tantalum and copperbetween the structures from over the active surface of the semiconductordevice being fabricated. Slurries that are used in copper CMP processestypically have a pH of about 7.0. Many of these slurries includehydrogen peroxide (H₂O₂) as an oxidizing agent. Since hydrogen peroxidereadily generates hydroxy free radicals (OH), hydrogen peroxide is avery strong oxidizing agent. Tantalum, however, is substantiallychemically inert Thus, the oxidizers of CMP slurries that remove copperdo not effectively oxidize tantalum and, thus, do not adequately effectthe removal of tantalum. Likewise, slurries that are useful for removingtantalum by CMP processes are likewise not effective for removingcopper. As a result, when conventional CMP processes are used to isolatethe tantalum-copper conductive structures of a semiconductor device, twoseparate slurries must be used.

It has been proposed that tungsten be used in place of tantalum insemiconductor devices as a barrier material for copper conductivestructures. Nonetheless, when known copper CMP slurries are used tosubstantially simultaneously CMP tungsten and copper, the tungstenbarrier layer may dissolve, or be removed, at a faster rate than thecopper. This is at least partially because, as the following chemicalequations illustrate, tungsten (W) is more readily oxidized than copper(Cu):W+2H₂O→4H++4e⁻+WO₂ E ₀=0.12;Cu→Cu²⁺+2e ⁻ E ₀=−0.34.

Thus, in conventional slurries, although both copper and tungsten aresimultaneously exposed to the same oxidants, the tungsten will typicallybe oxidized first. As a result, gaps may form in locations where thebarrier material should be located between copper conductive structuresand adjacent portions of the semiconductor device structure upon whichthe conductive structures are being fabricated.

This phenomenon is illustrated in the electron micrograph of FIG. 1,which illustrates a semiconductor device structure 10 that includes theportions of a copper layer 20 and an underlying tungsten barrier layer18 disposed within a recess 14 formed in an active surface 16 of asubstrate 12 of semiconductor device structure 10 following CMP thereofusing an alumina fixed-abrasive polishing pad and a copper CMP slurryhaving a pH of about 7. Once an interface 19 between barrier layer 18and copper layer 20 was exposed during the CMP process, tungsten ofbarrier layer 18 was oxidized and dissolved at a faster rate than theadjacent copper of copper layer 20, leaving a gap 21 between copperlayer 20 and adjacent regions of substrate 12, as well as undesirablypermitting copper of copper layer 20 to contact and, possibly, diffuseinto, unprotected adjacent regions of substrate 12.

Therefore, it would is desirable to provide a slurry that is useful inCMP processes and that effectively polishes or planarizes both copperand tungsten without causing oxidation or dissolution of the tungsten.

SUMMARY OF THE INVENTION

The present invention includes a method for substantially simultaneouslychemical-mechanical polishing a copper conductive structure and anadjacent barrier layer with a polishing pad, as well as slurries thatare useful for substantially simultaneously polishing a copperconductive structure and a barrier layer adjacent thereto.

The method of the present invention includes employing a polish padalong with a liquid polishing formulation, which is generally referredto herein as a slurry. The slurry is formulated to oxidize copper and amaterial of the barrier layer, such as tungsten, at substantially thesame rates and without preference between the two materials. Thus, in aslurry incorporating teachings of the present invention, the oxidationenergies of copper and the barrier material are substantially the same.Preferably, in the slurry, the oxidation energy of a barrier material,such as a tungsten-containing material (e.g., tungsten (W) and tungstennitride WN_(x)) is about 0.25 volt greater to about 0.2 volt less thanan oxidation energy of copper. As copper and the barrier material areoxidized by the slurry at about the same rates, use of a slurry soformulated to substantially simultaneously polish a copper conductivestructure and an adjacent barrier layer, prevents dissolution of thebarrier layer.

Slurries that are useful in the method of the present invention includeat least one oxidizer, at least on inhibitor, and one or more abrasives,and optionally but preferably one or more complexing agents. Therelative amounts of the oxidizer, inhibitor, abrasive, and optionalcomplexing agent, are balanced so as to facilitate substantiallyconcurrent polishing of a copper structure and another structureadjacent thereto, such as a barrier layer formed from atungsten-containing material. Thus, the slurry is formulated such thatthe relative amounts of the oxidizer, inhibitor, abrasive, and optionalcomplexing agent, to oxidize copper and a barrier material, such as atungsten-containing material, at substantially the same rates, or suchthat the oxidation energies of copper and the barrier material aresubstantially the same in the slurry, and to polish or planarize thesurface of the wafer or other structure. The pH of the slurry is also beoptimized so as to provide for oxidation of copper and a barriermaterial, such as a tungsten-containing material, at substantially thesame rates.

With such exemplary solutions in accordance with the invention receivedintermediate the wafer and polishing pad, the copper comprising layer ischemical-mechanical polished with slurry and the polishing pad. Theslurries can be utilized with a conventional planarizing machine knownand used in the art for chemical-mechanical polishing a semiconductorwafer.

The present invention also includes a system for substantiallysimultaneously polishing a copper conductive structure and an adjacentbarrier layer of a semiconductor device. Such a system includes apolishing pad and a slurry according to the invention, within whichcopper and the material of the barrier layer are oxidized atsubstantially the same rates, or have substantially the same oxidationenergies.

Other features and advantages of the present invention will becomeapparent to those of ordinary skill in the art through consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is an electron micrograph illustrating the dissolution of regionsof a tungsten barrier layer that underlie a copper structure of asemiconductor device structure when a conventional slurry is used tosimultaneously remove the copper and tungsten;

FIGS. 2–5 schematically illustrate an exemplary embodiment of apolishing method in which copper and a barrier material therefor aresubstantially simultaneously removed from a semiconductor devicestructure at substantially the same rates; and

FIG. 6 is a schematic representation of an exemplary embodiment of asystem that employs a polishing pad and a slurry to effect the method ofthe present invention.

FIG. 7 is a schematic representation of an exemplary embodiment of asystem that employs a web-format planarizing machine to effect themethod of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method incorporating teachings of the present invention is illustratedin FIGS. 2–5. With reference to FIG. 2, a semiconductor device structure10 including a substrate 12, which includes a recess 14 formed in anactive surface 16 thereof. A barrier layer 18 of a material, such as atungsten-containing material, that prevents copper from diffusing intoadjacent insulative regions of semiconductor device structure 10 locatedon active surface 16 and on the surfaces 15 of recess 14. Preferably,the tungsten-containing material comprises greater than about 50%tungsten. Exemplary tungsten-containing materials include tungsten (W)and tungsten nitride having the formula WN_(x). A copper layer 20 isformed over and contacts barrier layer 18. Copper layer 20 alsosubstantially fills recess 14. Although substrate 12 may include variousother structures beneath recess 14, barrier layer 18, and copper layer20, for purposes of simplicity, no additional structures are illustratedin the semiconductor device structure 10 shown in FIGS. 2–5.

In forming a conductive structure from copper layer 20, portions ofcopper layer 20 and of barrier layer 18 that are not located withinrecess 14 must be removed from semiconductor device structure 10. Asdiscussed previously herein, CMP processes are typically used to removeunwanted portions of copper layers. With reference to FIG. 3, a slurry30 is applied over copper layer 20. A polishing pad 40, which may beembodied as a conventional polishing pad, a web-type polishing pad, abelt-type polishing pad, or in any other polishing pad format known inthe art, is then brought into frictional contact (e.g., by rotation ofsemiconductor device structure 10 or movement of the polishing pad 40)with copper layer 20 to, along with slurry 30, remove copper layer 20.An inhibitor component 32 of slurry 30 fills recessed areas 22 of copperlayer 20, thereby preventing removal of material from recessed areas 22until material of higher areas 24 of copper layer 20 has been removed.

Eventually, regions of barrier layer 18 overlying active surface 16 areexposed through copper layer 20, as shown in FIG. 4. At this point,slurry 30 and polishing pad 40 remove the material or materials ofbarrier layer 18 and the copper of copper layer 20 at substantially thesame rates.

Barrier layer 18 is removed from active surface 16 by continuedpolishing with slurry 30 and polishing pad 40. Once barrier layer 18 issubstantially removed from active surface 16 and the surface 26 of theportion of copper layer 20 that remains within recess 14 is locatedsubstantially in the plane of active surface 16, as depicted in FIG. 5,the polishing process is terminated. As illustrated in FIG. 5, theremaining portion of barrier layer 18 substantially lines recess 14 andseparates the remaining portion of copper layer 20 from adjacentportions of substrate 12.

In order to effect removal of copper and the material or materials(e.g., tungsten-containing material) of an adjacent barrier layer 18 orother structure by CMP at substantially the same rates, slurry 30 isformulated so as to oxidize copper and the material or materials of theadjacent barrier layer 18 at substantially the same rates. Statedanother way, copper and the material or materials (e.g.,tungsten-containing material) of the adjacent barrier layer 18 havesubstantially the same oxidation energies in slurry 30. As a result, asan interface 19 between layers 18 and 20 is exposed to slurry 30, thematerial or materials of barrier layer 18 will not dissolve, or beremoved from semiconductor device structure 10, at a significantlygreater rate than copper or copper layer 20 is dissolved, or removedfrom semiconductor device structure 10. To achieve the desired removal,the oxidation energy of the tungsten-comprising material in slurry 30 ispreferably about 0.25 volt more to about 0.2 volt less than theoxidation energy of copper in slurry 30.

Slurry 30 includes an oxidizer component, which oxidizes both the copperof copper lay 20 and the material or materials (e.g.,tungsten-containing material) of barrier layer 18 so as to chemicallysoften these materials and to thereby facilitate their mechanicalremoval from semiconductor device structure 10 by polishing pad 40.Slurry 30 includes an inhibitor component 32, which prevents recessed,or lower, areas 22 of copper layer 20 from being removed until higherareas 24 of copper layer 20 have been removed down to substantially thesame plane. Slurry 30 further includes an abrasive agent, which effectsthe mechanical part of the CMP process to abrade and polish or planarizethe surface of the semiconductor device 10, in combination withpolishing pad 40. As a result, the continued oxidation of materiallayers 18, 20 by slurry 30 may occur at optimal rates and, thus, therates at which the materials of layers 18 and 20 are removed fromsemiconductor device structure 10 may also be optimized.

According to the invention, to achieve an optimal and balanced rate ofremoval of the copper and tungsten-containing barrier layers atsubstantially the same rates, and without preferential etching of onematerial over the other, the slurry is formulated to achieve a ΔE rangeof about 0.05 eV to about 0.20 eV, by optimizing the oxidizer componentand the pH of the slurry.

The amount of oxidizer included in the slurry is controlled to maintainan about equal rate of selectivity between the copper of copper layer 20and the material or materials (e.g., tungsten-containing material) ofbarrier layer 18. Examples of oxidizers that are useful as the oxidizercomponent of slurry 30 include, without limitation, hydrogen peroxide,ammonium persulfate, potassium iodate, potassium permanganate, ferricnitrate, and cerium (IV) compounds such as ceric nitrate and cericammonium nitrate, bromates, chlorates, chromates, and iodic acid, andmixtures thereof. The oxidizer component preferably comprises about0.05% to about 10% by weight of slurry 30, preferably about 0.1% toabout 5.0% by weight, more preferably about 3% to about 5% of the weightof slurry 30. The oxidizing agent is preferably not as strong as, forexample, hydrogen peroxide or an organic peroxide such asmonopersulfates, which have a relatively high static etch rate of thetungsten-containing material. Thus, a “dual” oxidizer can be usedcomprising the foregoing oxidizing agents combined with a minimal amountof hydrogen peroxide or ammonium persulfate, of about 0.001% to about 1%to about 2% by weight of the slurry.

Examples of useful copper corrosion inhibitors 32 include azoles such asimidazole, benzotriazole, benziimidazole, benzothizole,mercaptabenzothiazole and tolytriazole, and other azole derivatives withhydroxy, amino, imino, carboxy, mercapto, nitro and alkyl substitutedgroups; urea and thiourea; amines such as methylamine and diethylamine;ring compounds such as pyridine, quinoline, and dicyclohexamine nitrite;other compounds such as potassium silicate, ammonium borate, ammoniumphosphate and potassium dichromate; and mixtures thereof. Inhibitorcomponent 32 of slurry 30 preferably includes an azole compound, such asbenzenetriazole (BTA). While inhibitor component 32 may make up about0.05% to about 2% by weight of slurry 30, it is preferred the inhibitorcomponent 32 comprise about 0.05% to about 0.2% by weight of slurry 30.For example, slurry 30 may include about 0.1% BTA, by weight.

Examples of useful abrasive agents include, but are not limited to,alumina (Al₂O₃), titanium dioxide (TiO₂), silicon dioxide (SiO₂), andcerium dioxide (CeO₂). The abrasive preferably comprises about 0.5% toabout 10% by weight of slurry 30.

Slurry 30 can have a pH in the range of about 3 to about 7, but the pHof slurry 30 is optimally in the range of about 3 to about 5. One ormore pH control agents or buffers may be used, as known in the art, toadjust the pH of slurry 30 to a desired level. Preferably, the pHcontrol agent will adjust the pH of slurry 30 to a desirable range orpoint without significantly etching the insulator (e.g.,borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), orborosilicate glass (BSG)) that underlies the layer or layers beingpolished. Examples of useful pH control agents include potassiumhydrogen phthalate, ammonium phosphate, ammonium acetate, ammoniumdihydrogen phosphate, dibasic ammonium citrate, ammonium hydrogenphosphate, tribasic ammonium citrate, ammonium oxalate, ammoniumcarbamate, acetic acid, phosphoric acid, and sulfuric acid, amongothers, and mixtures thereof.

In a preferred embodiment, slurry 30 also includes one or morecomplexing agents, which complex with ions of the layers 18, 20 beingremoved (e.g., copper ions from copper layer 20) so as to facilitate thedissolution of these reactant ions, allowing these reactant ions to bemoved away from the locations at which layers 18 and 20 are beingoxidized. Examples of suitable complexing agents of slurry 30 mayinclude, but are not limited to, glycine, ammonium citrate, ammoniumphosphate, ammonium acetate, ammonium thiocyanate, and 2,4-pentadione,and combinations thereof. Slurry 30 preferably includes about 1% toabout 10% of the one or more complexing agents, by weight of slurry 30,more preferably about 3% to about 5% by weight of slurry 30. Forexample, slurry 30 may include about 1% of the complexing agent glycine,including a concentration of 0.1 M (molar) polyethylene glycol (PEG), byweight of slurry 30. As another example, slurry 30 may include about 3%ammonium acetate, by weight.

The slurry solution can also comprise one or more surfactants, forexample present at a concentration of from about 1% to about 10% byvolume. Example surfactants include dodecyl sulfate sodium salt, sodiumlauryl sulfate, dodecyl sulfate ammonium salt, polyethylene glycol,polyoxyethylene ether, glycerol, polypropylene glycol, polyoxyethylenelauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearylether, polyoxyethylene oleyl ether, and mixtures thereof. The slurry canfurther comprise one or more thickeners to achieve a desired viscosity,with an example preferred range being from about 10 centipoise to about20 centipoise at room temperature. Examples of suitable thickenersinclude Polyox™ available from Union Carbide of Danbury, Conn., andCarbopol™ available from B. F. Goodrich of Cleveland, Ohio.

The specific amounts of the components of slurry 30 may be determined byidentifying slurry 30 formulations in which copper gives up electrons atsubstantially the same rate as a barrier material, such atungsten-containing material, of a barrier layer 18 to be polishedsubstantially simultaneously with copper layer 20. Stated another way,slurry 30 may be formulated so that copper and a barrier materialtherefor, such as a tungsten-containing material, have the substantiallysame oxidation energies therein, or are oxidized at substantially thesame rates therein. Preferably, the oxidation energy of thetungsten-containing material or another barrier material in slurry 30 iswithin the range of about 0.25 volt more than to about 0.2 volt lessthan the oxidation energy of copper in slurry 30, the range includingthe end point values thereof. These formulations of slurry 30 willfacilitate the removal of copper and a barrier material, such as atungsten-containing material, from a semiconductor device structure 10at substantially the same rates.

Slurry 30 formulations having these characteristics may be determined asknown in the art, such as by measuring the open circuit potentials ofcopper and a barrier material, such as tungsten, in slurry 30.

Referring now to FIG. 6, a polishing system 50 for effecting thesubstantially simultaneous polishing of copper and an adjacent barriermaterial in accordance with the method of the present invention isillustrated. Polishing system 50 includes a polishing apparatus 42,which supports or carries a polishing pad 40, and a substrate support 44configured to hold a semiconductor device structure 10, to bring thesame into frictional contact with polishing pad 40, and, preferably, torotate semiconductor device structure 10 relative to polishing pad 40.Polishing system 50 also includes a slurry applicator 46 and a rinsingelement 48.

Any known CMP apparatus, including conventional, rotary CMP apparatus,web format CMP apparatus, and belt format CMP apparatus, may comprisepolishing apparatus 42, substrate support 44, slurry applicator 46, andrinsing element 48 of polishing system 50.

Conventional CMP pads are round, planar, and have larger dimensions thanthe semiconductor substrates (e.g., wafers or other substrates includingsilicon, gallium arsenide, indium phosphide, etc.) upon which thestructures or layers to be planarized or otherwise polished have beenformed. In polishing one or more layers or structures formed on asubstrate, the substrate and the conventional CMP pad are rotatedrelative to one another, with the location of the substrate being movedcontinuously relative to the polishing surface of the pad so thatdifferent areas of the pad are used to polish one or more of the layersor structures formed on the substrate.

In use of polishing system 50, one or more semiconductor devicestructures 10 having one or more layers thereon that are to bechemical-mechanical polished are secured to substrate support 44. Ifnecessary, polishing pad 40 is also secured to polishing apparatus 42.Slurry 30 from a slurry source 47 is introduced by slurry applicator 46onto semiconductor device structure 10 and, once slurry 30 has beenapplied, one or both of semiconductor device structure 10 and polishingpad 40 are substantially continuously laterally moved (e.g., rotate orvibrated or otherwise moved side-to-side) and brought into frictionalcontact with one another so as so effect the CMP process.

In some instances, it would be desirable to maintain a temperature at orbelow room temperature during the copper polish (i.e., at or below 74°F. to about 65° F.). This is seldom practical where lower slurrytemperature will also result in poor abrasive material dispersalthroughout the slurry during polish. Accordingly, elevated temperaturesare utilized during the polish. Polishing in all embodiments preferablyis conducted at atmospheric pressure and anywhere from 40° F. up to 145°F., although other conditions are of course possible.

Once the desired portions of one or more layers 18, 20 (FIGS. 2–5) havebeen removed from semiconductor device structure 10, semiconductordevice structure 10 is moved away from polishing pad 40 and slurry 30remaining on semiconductor device structure 10 is rinsed therefrom by arinse liquid 49 from rinsing element 48. Subsequent fabricationprocesses may then be conducted on semiconductor device structure 10, asknown in the art.

Another polishing format is the so-called “web” format, wherein the padhas an elongate, planar configuration. The web is moved laterally from asupply reel to a take-up reel so as to provide “fresh” areas thereof forpolishing one or more layers or structures formed on a semiconductorsubstrate. A similar, newer, polishing format is the so-called “belt”format, wherein the pad is configured as a belt, or continuous loop, ofpolishing material. In both the “web” and “belt” formats, thesemiconductor substrate is rotated or revolved upon being brought intocontact with the pad. The pad is moved when a “fresh” polishing surfaceis needed or desired.

Example equipment and processing utilized in accordance with theinvention is described with reference to FIG. 7, wherein a web-formatplanarizing machine 60 is used for chemical-mechanical polishing asemiconductor wafer (not shown). Planarizing machine 60 has a supporttable 62 with a top panel 64 at a work station where an operativeportion (A) of a planarizing pad 40′ is positioned. The top-half panel64 is generally a rigid plate to provide a flat, solid surface to whicha particular section of planarizing pad 40′ may be secured duringpolishing.

Planarizing machine 60 also has a plurality of rollers to guide,position and hold planarizing pad 40′ over top panel 64. The rollersinclude a supply roller 68, first and second idler rollers 70 a and 70b, first and second guide rollers 72 a and 72 b, and a take-up roller74. The supply roller 68 carries an unused or pre-operative portion ofthe planarizing pad 40′, and take-up roller carries a used orpost-operative portion of planarizing pad 40′. First idler roller 70 aand first guide roller 72 a stretch planarizing pad 40′ over top panel64 to hold the planarizing pad 40′ stationary during operation.Planarizing pad 40′ in accordance with the invention preferablycomprises a fixed abrasive pad, such as described above, and having alength greater than a maximum diameter of the wafers being polished. Amotor (not shown) derives at least one of supply roller 68 and take-uproller 74 to sequentially advance the planarizing pad 40′ across thetop-panel 64. As such, clean pre-operative sections of the planarizingpad 40′ may be quickly substituted for used sections to provide aconsistent surface for planarizing and/or cleaning the substrate.

The web-format planarizing machine 60 has a carrier assembly 76 thatcontrols and protects the wafer during polishing. Carrier assembly 76generally has a substrate holder 78 to pick up, hold and release thewafer at appropriate stages of the polishing cycle. A plurality ofnozzles 80 attached to substrate holder 78 dispense a planarizingsolution 30′ in accordance with the invention onto a planarizing surface82 of planarizing pad 40′. Carrier assembly 76 also generally has asupport gantry 84 carrying a drive assembly 86 that translates alonggantry 84. Drive assembly 86 generally has an actuator 88, a drive shaft90 coupled to the actuator 88, and an arm 92 projecting from drive shaft90. Arm 92 carries substrate holder 78 via another shaft 94 such thatdrive assembly 86 orbits substrate holder 78 about an axis B—B offsetfrom a center point C—C of the wafer.

In accordance with an aspect of the invention, the process preferablycomprises moving web/pad 40′ a distance less than the maximum diameterof the wafer such that a subsequently polished wafer is exposed to afresh pad segment which was not utilized to polish the immediatelypreceding wafer. Preferably, the distance moved is less than or equal toabout 1.0% of the maximum diameter for uniformity of polish and toextend life of the pad. For example for an 8-inch diameter wafer, anincremental movement of pad/web 40′ between each polishing is about 0.25inch.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents. The complete disclosures of all patents, patent documents,and publications listed herein are incorporated by reference, as if eachwere individually incorporated by reference.

1. A solution for CMP processing of a semiconductor substrate, thesolution comprising: effective amounts of about 3–10% by weight of anoxidizer and about 0.05–0.2% by weight of an inhibitor to remove acopper material and a tungsten barrier material from the semiconductorsubstrate at about the same rate, the solution having a pH of about 3–7.2. The solution of claim 1, wherein the oxidizer is selected from thegroup consisting of an ammonium compound, a nitrate compound, and anamine compound.
 3. The solution of claim 1, wherein the oxidizer isselected from the group consisting of hydrogen peroxide, potassiumiodate, potassium permanganate, ammonium persulfate, ammonium molybdate,ferric nitrate, nitric acid, potassium nitrate, and ammonia.
 4. Thesolution of claim 1, comprising about 1–10% complexing agent by weightof the solution.
 5. The solution of claim 1, further comprising athickener.
 6. The solution of claim 1, further comprising a pH controlagent.
 7. The solution of claim 6, wherein the pH control agent isselected from the group consisting of potassium hydrogen phthalate,ammonium acetate, ammonium oxalate, ammonium carbamate, ammoniumphosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate,dibasic ammonium citrate, tribasic ammonium citrate, acetic acid,phosphoric acid, and sulfuric acid.
 8. The solution of claim 1, furthercomprising an abrasive.
 9. The solution of claim 8, wherein the abrasiveis selected from the group consisting of alumina, titanium dioxide,silicon dioxide, and cerium dioxide.
 10. The solution of claim 8,comprising about 0.05–10% by weight abrasive.
 11. The solution of claim1, further comprising a complexing agent.
 12. The solution of claim 11,wherein the complexing agent is selected from the group consisting ofglycine, ammonium citrate, ammonium phosphate, ammonium acetate,ammonium thiocyanate, and 2,4-pentadione.
 13. The solution of claim 1,further comprising a surfactant.
 14. The solution of claim 13, whereinthe surfactant is selected from the group consisting of polyethyleneglycol, polyoxyethylene ether, glycerol, polypropylene glycol,polyoxyethylene lauryl ether, polyoxyethylene cetyl ether,polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether.
 15. Asolution for CMP processing of a semiconductor substrate, the solutioncomprising: an oxidizer in combination with about 0.05–0.2% by weight ofan inhibitor in amounts effective to remove a copper material and atungsten barrier material from the semiconductor substrate at about thesame rate, the solution having a pH of about 3–7.
 16. A solution for CMPprocessing of a semiconductor substrate, the solution comprising:effective amounts of an oxidizer and an inhibitor selected from thegroup consisting of benzotriazole, mercaptabenzothiazole, tolytriazole,methylamine, diethylamine, pyridine, quinoline, dicylohexamine nitrate,potassium silicate, ammonium borate, ammonium phosphate, and potassiumdichromate, to remove a copper material and a tungsten barrier materialfrom the semiconductor substrate at about the same rate, the solutionhaving a pH of about 3–5.
 17. The solution of claim 16, comprising about0.05–10% by weight oxidizer and about 0.05–2% inhibitor.
 18. A solutionfor CMP processing of a semiconductor substrate, the solutioncomprising: about 0.05–10% of an oxidizer and about 0.05–2% by weight ofan inhibitor selected from the group consisting of benzotriazole,mercaptabenzothiazole, tolytriazole, methylamine, diethylamine,pyridine, quinoline, dicylohexamine nitrate, potassium silicate,ammonium borate, ammonium phosphate, and potassium dichromate, to removea copper material and a tungsten barrier material from the semiconductorsubstrate at about the same rate; the solution having a pH of about 3–7.19. A solution for CMP processing of a semiconductor substrate, thesolution comprising: effective amounts of about 3–5% by weight of a dualoxidizer and about 0.05–0.2% by weight of an inhibitor to remove acopper material and a tungsten-containing barrier material from thesemiconductor substrate at about the same rate, the dual oxidizercomprising a first oxidizer, and up to about 2% by weight of a secondoxidizer selected from the group consisting of hydrogen peroxide andammonium persulfate, the solution having a pH of about 3–7.
 20. Asolution for CMP processing of a semiconductor substrate, the solutioncomprising: effective amounts of about 3–10% by weight of a firstoxidizer and a second oxidizer, and about 0.05–0.2% by weight of aninhibitor to remove a copper material and a barrier material from thesemiconductor substrate at about the same rate; wherein the firstoxidizer is selected from the group consisting of potassium iodate,potassium permanganate, ferric nitrate, cerium (IV) compounds, bromates,chlorates, chromates, iodic acid, ammonium molybdate, nitric acid,potassium nitrate, amine compounds, and ammonia; the second oxidizer isselected from the group consisting of hydrogen peroxide and ammoniumpersulfate; and the solution comprises about 2% by weight or less of thesecond oxidizer, and has a pH of about 3–7.
 21. A solution for CMPprocessing of a semiconductor substrate, the solution comprising: aninhibitor, about 3–10% by weight of a first oxidizer and a secondoxidizer including a minimal amount up to about 2% by weight of thesecond oxidizer selected from the group consisting of hydrogen peroxideand ammonium persulfate, to remove a copper material and a barriermaterial from the semiconductor substrate at about the same rate; thesolution having a pH of about 3–7.
 22. A solution for CMP processing ofa semiconductor substrate, the solution comprising: about 3–10% byweight of a first oxidizer and a second oxidizer including about0.001–2% of the second oxidizer, and about 0.05–0.2% by weight of aninhibitor to remove a copper material and a barrier material from thesemiconductor substrate at about the same rate; wherein the firstoxidizer is selected from the group consisting of potassium iodate,potassium permanganate, ferric nitrate, cerium (IV) compounds, bromates,chlorates, chromates, iodic acid, ammonium molybdate, nitric acid,potassium nitrate, amine compounds, and ammonia; and the second oxidizeris selected from the group consisting of hydrogen peroxide and ammoniumpersulfate; and the solution has a pH of about 3–7.
 23. A solution forCMP processing of a semiconductor substrate, the solution comprising:effective amounts of about 3–10% by weight of an oxidizer and about0.05–0.2% by weight of an inhibitor to remove a copper material and abarrier material comprising about 50% tungsten or greater from thesemiconductor substrate at about the same rate, the solution having a pHof about 3–7.
 24. The solution of claim 23, wherein the barrier materialcomprises tungsten nitride.
 25. A solution for CMP processing of asemiconductor substrate, the solution comprising: a mixture of about3–10% by weight of an oxidizer, about 0.05–0.2% by weight of aninhibitor, and an abrasive; the oxidizer and inhibitor in amountseffective to remove a copper material and a tungsten barrier materialfrom the semiconductor substrate at about the same rate, the solutionhaving a pH of about 3 to about
 7. 26. The solution of claim 25, whereinthe abrasive is selected from the group consisting of alumina, titaniumdioxide, silicon dioxide, and cerium dioxide.
 27. The solution of claim25, comprising about 3–5% by weight oxidizer, and about 0.05–10% byweight abrasive.
 28. The solution of claim 25, further comprising a pHcontrol agent.
 29. A solution for CMP processing of a semiconductorsubstrate comprising a tungsten barrier material and a copper materialdisposed thereon, the solution comprising: effective amounts of about3–10% by weight of an oxidizer and about 0.05–0.2% by weight of aninhibitor to remove the tungsten barrier material at a slower rate thanthe copper material, the solution having a pH of about 3 to about
 7. 30.The solution of claim 29, wherein the relative amounts are balanced sothat a rate of removal of the tungsten barrier material by the slurry isabout up to about ten times slower than a rate of removal of copper bythe slurry.
 31. The solution of claim 29, wherein the relative amountsare balanced so that a rate of removal of the tungsten barrier materialby the slurry is about two to about four times less than a rate ofremoval of copper by the slurry.
 32. The solution of claim 29, wherein,in the slurry the copper material and the tungsten barrier material eachhave an oxidation energy, the oxidation energy of the tungsten barriermaterial being about 0.25 volt more to about 0.2 volt less than theoxidation energy of the copper material.
 33. The solution of claim 29,wherein the tungsten barrier material consists essentially of tungsten.34. The solution of claim 29, wherein the tungsten barrier materialcomprises greater than about 50% tungsten.
 35. The solution of claim 29,wherein the tungsten barrier material comprises tungsten nitride. 36.The solution of claim 29, having a pH of about 3 to about
 5. 37. Asolution for CMP processing of a semiconductor substrate comprising atungsten barrier material and a copper material disposed thereon, thesolution comprising: a mixture of about 3–10% by weight of an oxidizer,about 0.05–0.2% by weight of an inhibitor, and an abrasive; the oxidizerand inhibitor in amounts effective to remove the tungsten barriermaterial at a slower rate than the copper material, the solution havinga pH of about 3 to about 7.